Unico vs SpacePak: A Milwaukee Installer's Honest Comparison

After installing both SpacePak and Unico high-velocity systems in Wisconsin homes for decades, we get this question a lot: Which one is better?

It is a fair question. From the outside, the two products look almost identical — same small-duct concept, same 2-inch flexible tubing, same small round outlets in your ceiling or floor. If you are getting quotes from multiple contractors, you may see one bidding Unico and another bidding SpacePak and wonder what the difference actually is.

We are going to give you our honest answer, based on years of installing, servicing, and troubleshooting both systems in Milwaukee-area homes. Burkhardt Heating, Cooling, Plumbing & Electric has been a family-owned business since 1961. We have installed high-velocity AC since the technology entered the residential market. This is not a manufacturer's comparison chart. It is what we have actually seen.

How Both Systems Work

Unico and SpacePak both fall into the Small-Duct High-Velocity (SDHV) category. The core concept is the same for both:

Small, flexible supply ducts. Instead of the large rectangular ducts used in conventional systems — typically 8 to 12 inches across — SDHV systems use flexible tubing just 2 to 2.5 inches in diameter. This tubing routes through wall cavities, across attic floor framing, and around obstacles that would require major carpentry with conventional ductwork.

High-velocity delivery. Air is delivered to conditioned spaces through small round outlets (typically 5 inches in diameter) at higher velocity than a conventional register. The result is the aspiration effect: the fast-moving air stream draws room air into the mix, which promotes thorough air circulation and eliminates the hot and cold pockets common in larger duct systems.

Superior dehumidification. Both systems move air at approximately 200 CFM per ton — about half the airflow of a conventional system. This slower airflow across a thicker evaporator coil gives more contact time for moisture removal. SDHV systems pull significantly more humidity out of the air per cooling cycle compared to conventional equipment, which is a meaningful advantage in Milwaukee's July and August weather.

Retrofit-first design. Both products were developed specifically for homes without existing ductwork — the pre-war, boiler-heated housing stock that makes up large portions of Whitefish Bay, Shorewood, Wauwatosa, and the Milwaukee East Side. That origin shows in how they are engineered: small, flexible, and designed to fit where nothing else can.

Where the Two Are Similar

Before getting to differences, it is worth acknowledging that Unico and SpacePak share a lot of common ground — and both are legitimate solutions for homes that cannot accommodate conventional ductwork.

Both are small-duct high-velocity systems. The fundamental installation approach is the same. Two-inch flex tubing, a central air handler, a plenum, and small outlets at the end of each run.

Both work alongside boiler heating. Neither system replaces your boiler. They install as independent cooling-only systems, leaving your existing radiator heat intact. If you are in Shorewood and you have a 1927 hot-water boiler that heats the home perfectly well, either system works alongside it without conflict.

Both are genuinely quiet when installed correctly. The outlet sound in a properly designed SDHV system — the gentle rushing of air — is typically quieter than a window unit and less intrusive than a conventional forced-air register. Noise issues with either brand trace almost exclusively to under-outletted designs or missing sound attenuators, not to the systems themselves.

Both are retrofit-proven. Contractors have been installing both products in older homes for decades. There is a track record with both on performance, longevity, and homeowner satisfaction when the installation is done right.

Where We Saw Real Differences in the Field

This is the part most comparison articles skip. We are not going to skip it, but we are also going to be precise about what we mean.

Our observations here come from years of installing both systems and then, critically, from years of servicing both systems. The difference between a brand-new installation and a system at year seven, year ten, or year fifteen is where you learn what actually holds up.

Air handler and coil construction. Over time, we found that Unico's air handlers and coil assemblies held up consistently across installations in our service area. The construction quality and the approach to moisture management in the coil assembly contributed to long, reliable service lives. This is a general observation from field experience across many systems, not an isolated incident.

Control system reliability. Unico's S.M.A.R.T. (Software Managed Air Rate Technology) control board manages airflow rates and system operation. In our experience, this system has been consistent and predictable over long periods. When something did need attention, Unico's technical support team was responsive and effective.

Parts availability and support. A system installed in a Milwaukee home today needs to be serviceable ten or fifteen years from now. Parts availability and manufacturer support over time are factors we weigh seriously when we decide what to install. Unico's support infrastructure — including their Preferred Contractor program and technical support team — has been a reliable resource for us.

We want to be careful here: we are not saying SpacePak is a bad system or that every SpacePak installation has problems. That is not our experience, and it would not be an honest statement. What we can say is that when we looked honestly at long-term durability and parts reliability based on our service experience, Unico consistently came out ahead. That assessment — made over years, not months — is what led us to change our installation practice.

Why We Now Install Unico Exclusively

After installing both SpacePak and Unico for years, we now install Unico exclusively. We have found Unico's air handlers, coils, and control systems offer the durability and long-term reliability our customers expect. We continue to service existing SpacePak systems for homeowners who already have them.

This was a considered business decision, not a reactive one. Our customers in Whitefish Bay, Shorewood, Wauwatosa, and the East Side are investing in homes they plan to own and live in for decades. When we put a system in a 1925 Colonial Revival in Whitefish Bay, we want to be confident that we will still be servicing it in 2035 and 2040 — and that the system will still be performing. Unico is the product that gives us that confidence.

As a Unico Preferred Contractor, we have also invested in factory training at Unico's St. Louis facility, which gives our technicians direct access to Unico's engineering and training teams. That relationship matters for installations and for support when unusual situations arise in the field.

We Still Service Your SpacePak System

If you have a SpacePak high-velocity system and you are looking for service, maintenance, or repair — we work on SpacePak equipment. We carry common SpacePak parts, our technicians are trained on the equipment, and we are not going to tell you that you need to replace a working system.

If your SpacePak system is aging and you are weighing repair costs against replacement, we will give you a straightforward assessment. We will look at the system's age, the repair scope, and the realistic remaining service life, and give you an honest answer about whether it makes more sense to repair or replace. If replacement is the right call, we will quote you a Unico installation. If repair is the right call, we will do the repair.

How to Decide for Your Milwaukee Home

If you are choosing between Unico and SpacePak for a new installation, here is our practical guidance:

If you are getting a new installation: We install Unico, and we stand behind it. The system's long-term reliability, Unico's support infrastructure, and the 10-year limited parts warranty available through the Preferred Contractor program are all factors that benefit you as a homeowner.

If you already have a SpacePak system that is working well: There is no compelling reason to replace a functioning system. Keep maintaining it, keep it serviced, and get another decade or more of use out of it.

If you have an aging SpacePak system that needs major repair: This is where the comparison becomes relevant. Depending on the age of the system and the scope of the repair, a new Unico installation might be more economical over a 10-year horizon than continued repairs to aging equipment. We will help you run those numbers honestly.

If you are a buyer purchasing a Milwaukee home: Either system — if properly installed and maintained — is a legitimate asset. A home with a functioning high-velocity AC system is better positioned for our climate than one with only window units. Get the system inspected before closing so you know what you are inheriting.

The most important variable in any high-velocity installation is not the brand — it is the installer. A correctly sized, correctly routed, correctly commissioned system outperforms a poorly designed system of any brand.

Frequently Asked Questions

Is Unico more expensive than SpacePak to install?

The systems are comparable in installed cost. Equipment pricing for both brands is in a similar tier. Labor is the larger cost variable, and that is driven by your home's routing complexity and system size — not by which brand is specified. During a free in-home assessment, we quote the full project cost so you know what you are working with.

Can my Unico system cool the whole house, or just certain floors?

A single properly sized Unico system can typically cool an entire home up to about 3,500 square feet. Larger homes — or homes with very difficult routing between floors — sometimes benefit from two systems, one per zone. This is determined during the design phase. The sizing guide on our high-velocity AC service page has more detail.

Do Unico and SpacePak use the same outlets?

The outlet diameters and basic designs are similar, but they are not interchangeable. Unico outlets are designed for Unico tubing and airflow specs; SpacePak outlets are designed for SpacePak specs. If you are replacing a SpacePak system with Unico, new outlets are part of the installation.

How does high-velocity AC handle Milwaukee's humidity?

Very well — better than conventional systems, in fact. The SDHV design's slower airflow across a thicker coil removes significantly more moisture per cooling cycle. For East Side Milwaukee homes near the lakefront, where summer humidity can be persistently elevated, this performance advantage is meaningful. Homeowners often report that they run the system at 74°F instead of 70°F and still feel more comfortable than they did with window units.

What is the warranty on a new Unico installation by Burkhardt?

As a Unico Preferred Contractor, Burkhardt registers each installation with Unico within 90 days of completion, which qualifies the system for Unico's 10-year Limited Parts Warranty (extended from the standard 5-year warranty). Labor warranties are covered under Burkhardt's standard service agreement terms, which we review with you at the time of installation.

Ready to Talk Through Your Options?

Whether you are planning a new high-velocity installation or you have questions about an existing system, Burkhardt is the team to call. We have been doing this work in Milwaukee's historic neighborhoods longer than most, and we will give you a straight answer — not a sales pitch.

Call 414-206-3049 to schedule a free in-home assessment, or to talk through your situation before committing to anything. We serve Milwaukee, Washington, and Waukesha counties.

Learn more about our Unico installation process and pricing factors →